This proposal is directed toward examining the metabolic factors which regulate the formation of insoluble dextran by cariogenic Streptococcus mutans. Dextransucrase will be purified to homogeneity and characterized as to its subunit structure, active site, antigenic sites, and interactions with polysaccharide and cell-surface receptors. Mutants defective in insoluble dextran biosynthesis will also be sought and the enzymes from the mutants purified and compared with the wild- type enzyme. The purified enzyme will also be utilized to prepare antibody specifically directed against the enzyme. The site of synthesis of dextransucrase will be determined by assaying for the ability of subcellular fractions to incorporate C14-amino acids into proteins precipitable by specific antibody. This information together with the determination of the location of the cell-bound forms of the enzyme will be utilized to elucidate the mechanisms of synthesis and secretion of the enzyme. Finally, the mode of attachment of dextransucrase to the cell surface of S. mutans will be investigated as well as the possible role of this specie of the enzyme in cellular adherance to smooth surfaces. This information might be utilized to design negative effectors of insoluble dextran formation which could retard dental plaque formation.